Well known and successful German manufacturer of mobile homes “Carthago” opened a new sales maintenance and fabrication facility called “Carthago City” near Ravensburg (Southern Germany) in spring 2013.
One idea of the architectural concept was to provide a membrane covered area for exhibition and weather protected parking of brand-new mobile homes. Prime requirement was to protect the fairly expensive cars from hail during summer time.
Second request was to have a flexible modular system which allows expanding the covered area later by similar modules. So after a short preliminary design stage büro für leichtbau was assigned to develop 16x16m funnel shaped non-collapsible umbrellas.
Besides a satisfying overall visual appearance of the ensemble, which is almost granted by default when building funnel shaped umbrellas, our main focus was to develop a very reduced near minimized steel structure. In this special case it obviously makes sense to spend a little more time thinking of simplification and optimization because the design was meant to be built at least nine times.
One of the basic concepts of the structural design was to subdivide the umbrella into two main items: The shaft, which is a four-girder column with an additional drainage tube in the centre axis and the upper top-part including the circumferential frame with 12 radial suspended arms and the membrane surface with low-point ring.
This design allowed a very efficient and easy assembly and erection on site. In a first step the shaft is fixed and adjusted on cast-in embeds. Independently the upper part is assembled nearby on ground level on an auxiliary device which allows a very easy clamping of the outer membrane border to the frame. After pre-assembly on ground level the entire 16 x16m top element was lifted by mobile crane, fixed on the shaft and in a final step the low-point ring was pulled down to induce the necessary membrane pre-tension.
In a first stage approximate 2300m² modular roof covering was realised by 9 similar 16x16m non-collapsible umbrellas. The overall height of each umbrella is 10m with a non-overlapping circumferential membrane border at 7m. The gaps between the adjacent umbrellas are closed by metal-sheets. The funnel shaped umbrellas are made of primary steel structure S 355 and PVC-coated polyester membrane Type III (Ferrari 1202 S2).